The invention provides antistatic, thermoplastic moulding compositions with improved properties, based on optionally rubber-modified polymers of vinyl aromatics, e.g. styrene and/or xcex1-methyl styrene and acrylonitrile and/or acrylates, which contain a special acid-reacting polyether as the antistatic agent.
Most plastics, because of their chemical constitution, are electrical insulators with a high electrical surface resistance. This readily leads to the electrostatic charging of the plastics surfaces during the processing and use of such compositions. This results in various problems and drawbacks in practice, e.g. rapid soiling and accumulation of dust on plastics parts, with characteristic dust patterns forming on the surface. This is also true to a particular extent for optionally rubber-modified polymers of vinyl aromatics and acrylonitrile used as moulding compositions, e.g. styrene-acrylonitrile copolymers (SAN) and graft copolymers of styrene and acrylonitrile on polybutadiene (ABS).
The provision of antistatic properties in such moulding compositions is known. Alkyl and aryl sulfonates (DE-OS 1 544 652), amines (DE-PS 1 258 083), quaternary ammonium salts, amides, phosphoric acids and alkyl and aryl phosphonates, for example, are recommended as antistatic agents.
These antistatic moulding compositions still have drawbacks. Many of the antistatic agents mentioned are of low effectiveness and have to be used in high concentrations; many of these low molecular-weight compounds migrate to the surface. Mouldings with inhomogeneous and stained surfaces, or even surface deposits, are therefore often obtained. In many cases, mechanical properties such as e.g. heat resistance or modulus of elasticity are also severely impaired.
Even pure polyethers, as proposed e.g. in DE-PS 1 244 398 as high molecular-weight antistatic agents, have to be used in quantities of approx. 5 wt. % or more for the reliable provision of antistatic properties in styrene polymers. This leads to stained and greasy surfaces and even surface deposits on the finished parts.
Although the antistatic effect can be improved by graft copolymerisation of styrene and acrylonitrile on these polyethers, as described in EP-A-0 061 692, yellow to brown discolorations occur when processing styrene polymers containing such antistatic agents at temperatures of  greater than 150xc2x0 C.
The use of polyethers modified with radical formers according to EP-A-0 278 349 to impart antistatic properties to styrene polymers leads to improved effectiveness compared with the unmodified polyether, but the application is critical in respect of a quantitative decomposition of the radical former, characterised by high energy requirements and long reaction times, during the modification of the polyether to avoid undesirable side effects, especially discolorations and negative effects on the flow properties when soft and on the toughness of the moulding compositions containing them.
The object of the present invention was therefore to provide thermoplastic moulding compositions based on vinyl aromatic polymers with polyethers as antistatic agents without the above-mentioned disadvantages.
Surprisingly, it was found that the desired thermoplastic moulding compositions are obtained with very good antistatic properties if certain acid-reacting polyethers, preferably polyethers treated with certain carboxylic acids, are used as antistatic agents.
The invention provides antistatic, thermoplastic moulding compositions containing
I.) 99.8 to 95 parts by weight, preferably 99.5 to 96 parts by weight and particularly preferably 99 to 97 parts by weight of an optionally rubber-modified polymer of vinyl aromatics and optionally other vinyl monomers consisting of
A) 0 to 100 wt. % of one or more graft copolymers of 10 to 95 wt. % (based on A) rubber and 90 to 5 wt. % (based on A) monomers graft copolymerised on to the rubber, with styrene, xcex1-methyl styrene, ring-substituted styrene, methyl methacrylate, (meth)acrylonitrile, maleic anhydride, N-substituted maleimides or mixtures thereof being graft copolymerised as the monomers and the rubbers having glass transition temperatures of  less than 10xc2x0 C. and being present in the form of at least partially crosslinked particles with an average particle diameter (d50) of 0.05 to 20 xcexcm and
B) 100 to 0 wt. % of one or more thermoplastic vinyl polymers, the monomers being selected from the series styrene, xcex1-methyl styrene, ring-substituted styrene, methyl methacrylate, acrylonitrile, methacrylonitrile, maleic anhydride, N-substituted maleimides or mixtures thereof, and
II.) 0.2 to 5 parts by weight, preferably 0.5 to 4 parts by weight and particularly preferably 1 to 3 parts by weight of a polyalkylene ether with molecular weights (number average) of between 500 and 15,000 and a pH of 2.5 to 5.5, preferably of 3.0 to 5.0 (measured as a 5% dispersion in water), which preferably contains carboxyl groups.
The invention also provides a process for imparting antistatic properties to optionally rubber-modified polymers of vinyl aromatics and other vinyl monomers, as described above, which is characterised in that 0.2 to 5 parts of a polyalkylene ether with molecular weights (number average) of between 500 and 15,000 and a pH of 2.5 to 5.5 (measured as a 5% dispersion in water), which is a reaction product of polyols with one or more alkylene oxides and which is preferably prepared by mixing with 0.01 to 3 wt. %, preferably 0.02 to 2 wt. % and particularly preferably 0.05 to 1 wt. % (based on the quantity of polyalkylene ether) of at least one carboxylic acid and/or carboxylic anhydride and stirring at temperatures greater than or equal to room temperature, preferably at 20xc2x0 C. to 100xc2x0 C., particularly preferably 25 to 90xc2x0 C. and especially 30xc2x0 C. to 80xc2x0 C., are added to 99.8 to 95 parts by weight of polymer I.).
Optionally rubber-modified copolymers of vinyl aromatics and other vinyl monomers (I) within the meaning of the invention are mixtures of (A) 0 to 100, preferably 1 to 60, especially 5 to 50 wt. % of one or more graft copolymers and (B) 100 to 0, preferably 40 to 99, especially 50 to 95 wt. % of one or more thermoplastic vinyl polymers.
Graft copolymers (A) within the meaning of the invention are those in which either styrene, xcex1-methyl styrene, methyl methacrylate or a mixture of 95 to 50 wt. % styrene, xcex1-methyl styrene, ring-substituted styrene, methyl methacrylate or mixtures thereof and 5 to 50 wt. % (meth)acrylonitrile, maleic anhydride, N-substituted maleimides or mixtures thereof are graft copolymerised on to a rubber.
Suitable rubbers are practically all rubbers with glass transition temperatures of  less than 10xc2x0 C. Examples are polybutadiene, polyisoprene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylic rubbers, EPM rubbers (ethylene-propylene rubbers) and EPDM rubbers (ethylene-propylene-diene rubbers) containing an unconjugated diene, such as e.g. 1,5-hexadiene or norbornadiene, in small quantities as the diene. Diene rubbers are preferred.
The graft copolymers (A) contain 10 to 95 wt. %, especially 20 to 70 wt. %, rubber and 90 to 5 wt. %, especially 80 to 30 wt. %, graft copolymerised monomers. The rubbers are present in these graft copolymers in the form of at least partially crosslinked particles with an average particle diameter (d50) of 0.05 to 20 xcexcm, preferably 0.1 to 2 xcexcm and particularly preferably 0.1 to 0.8 xcexcm.
Graft copolymers of this type may be produced by radical graft copolymerisation of styrene, xcex1-methyl styrene, ring-substituted styrene, (meth)acrylonitrile, methyl methacrylate, maleic anhydride, N-substituted maleimide in the presence of the rubbers to be grafted. Preferred production processes are emulsion, solution, bulk or suspension polymerisation.
The average particle diameter d50 is the diameter above and below which 50 wt. % of the particles lie. It can be determined by ultracentrifuge measurement (W. Scholtan, H. Lange, Kolloid-Z. und Z. Polymere 250 (1972), 782-796).
The production of the copolymers and graft copolymers is generally known (cf. e.g. DE-OS 1 694 173 (=U.S. Pat. No. 3,564,077), DE-OS 2 348 377 (=U.S. Pat. No. 3,919,353), DE-OS 2 035 390 (=U.S. Pat. No. 3,644,574), DE-OS 2 228 242 (=GB 1 409 275).
The copolymers (B) may be built up from the graft monomers for (A) or similar monomers by polymerisation. especially from styrene. xcex1-methyl styrene, halostyrene, acrylonitrile, methacrylonitrile, methyl methacrylate, maleic anhydride, vinyl acetate, N-substituted maleimide or mixtures thereof. Copolymers of 95 to 50, preferably 60 to 80 wt. % styrene, xcex1-methyl styrene, methyl methacrylate or mixtures thereof with 5 to 50, preferably 40 to 20 wt. % acrylonitrile, methacrylonitrile, methyl methacrylate, maleic anhydride or mixtures thereof are preferred. Such copolymers are also formed as by-products during the graft copolymerisation. It is usual to add separately prepared copolymers in addition to the copolymers contained in the graft copolymer.
These do not have to be chemically identical with the ungrafted resin portions present in the graft copolymers. Suitable separately prepared copolymers are resinous, thermoplastic and rubber-free; copolymers of styrene and/or xcex1-methyl styrene with acrylonitrile, optionally in a mixture with methyl methacrylate, are especially suitable. Particularly preferred copolymers consist of 20 to 40 wt. % acrylonitrile and 80 to 60 wt. % styrene or xcex1-methyl styrene. Such copolymers are known and can be prepared especially by radical polymerisation, especially by emulsion, suspension, solution or bulk polymerisation. The copolymers preferably possess molecular weights of 15000 to 200000.
Apart from thermoplastic resins built up from vinyl monomers, it is also possible to use polycondensates, e.g. aromatic polycarbonates, aromatic polyester carbonates, polyamides as rubber-free copolymer in the moulding compositions according to the invention.
Suitable thermoplastic polycarbonates and polyester carbonates are known (cf. e.g. DE-AS 1 495 626, DE-OS 2 232 877, DE-OS 2 703 376, DE-OS 2 714 544, DE-OS 3 000 610, DE-OS 3 832 396, DE-OS 3 077 934), and can be produced e.g. by reacting diphenols of the formulae (III) and (IV) 
wherein
A is a single bond, C1-C5 alkylene, C2-C5 alkylidene, C5-C6 cycloalkylidene, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94SO2xe2x80x94 or xe2x80x94COxe2x80x94,
R5 and R6, independently of one another, denote hydrogen, methyl or halogen, especially hydrogen, methyl, chlorine or bromine,
R1 and R2, independently of one another, denote hydrogen, halogen, preferably chlorine or bromine, C1-C8 alkyl, preferably methyl, ethyl, C5-C6 cycloalkyl, preferably cyclohexyl, C6-C10 aryl, preferably phenyl, or C7-C12 aralkyl, preferably phenyl-C1-C4 alkyl, especially benzyl,
m is an integer from 4 to 7, preferably 4 or 5,
n is 0 or 1,
R3 and R4 are selectable for each X individually and, independently of one another, denote hydrogen or C1-C6 alkyl and
X signifies carbon,
with carbonic acid halides, preferably phosgene, and/or with aromatic dicarboxylic acid dihalides, preferably benzenedicarboxylic acid dihalides, by phase boundary poly-condensation or with phosgene by polycondensation in the homogeneous phase (the so-called pyridine process), it being possible to adjust the molecular weight by known means using an appropriate quantity of known chain terminators.
Suitable diphenols of formulae (III) and (IV) are e.g. hydroquinone, resorcinol, 4,4xe2x80x2-dihydroxydiphenyl, 2,2-bis(4-hydroxyphenyl)propane, 2,4-bis(4-hydroxyphenyl)-2-methylbutane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3-dimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5,5-tetramethylcyclohexane or 1,1-bis(4-hydroxyphenyl)-2,4,4-trimethylcyclopentane.
Preferred diphenols of formula (III) are 2,2-bis(4-hydroxyphenyl)propane and 1,1-bis(4-hydroxyphenyl)cyclohexane, and the preferred phenol of formula (IV) is 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.
Mixtures of diphenols can also be used.
Suitable chain terminators are e.g. phenol, p-tert.-butylphenol, long-chain alkylphenols such as 4-(1,3-tetramethylbutyl)phenol according to DE-OS 2 842 005, mono-alkylphenols, dialkylphenols with a total of 8 to 20 C atoms in the alkyl substituents according to DE-OS 3 506 472, such as p-nonylphenol, 2,5-di-tert.-butylphenol, p-tert.-octylphenol, p-dodecylphenol, 2-(3,5-dimethylheptyl)phenol and 4-(3,5-dimethylheptyl)phenol. The quantity of chain terminators required is generally 0.5 to 10 mole %, based on the sum of the diphenols (III) and (IV).
The suitable polycarbonates or polyester carbonates can be linear or branched; branched products are preferably obtained by incorporated 0.05 to 2.0 mole %, based on the sum of the diphenols used, of trifunctional or more than trifunctional compounds, e.g. those with three or more phenolic xe2x80x94OH groups.
The suitable polycarbonates or polyester carbonates can contain aromatically bonded halogen, preferably bromine and/or chlorine; they are preferably halogen-free.
They have average molecular weights ({overscore (M)}w, weight average), determined e.g. by ultracentrifugation or nephelometry, of 10000 to 200000, preferably 20000 to 80000.
Suitable thermoplastic polyesters are preferably polyalkylene terephthalates, i.e. reaction products of aromatic dicarboxylic acids or their reactive derivatives (e.g. dimethyl esters or anhydrides) and aliphatic, cycloaliphatic or arylaliphatic diols and mixtures of these reaction products.
Preferred polyalkylene terephthalates can be produced from terephthalic acids (or their reactive derivatives) and aliphatic or cycloaliphatic diols with 2 to 10 C atoms by known methods (Kunststoff-Handbuch, volume VIII, p. 695 ff., Carl Hanser Verlag, Munich 1973).
In preferred polyalkylene terephthalates, 80 to 100, preferably 90 to 100 mole % of the dicarboxylic acid radicals are terephthalic acid radicals and 80 to 100, preferably 90 to 100 mole % of the diol radicals are ethylene glycol and/or 1,4-butanediol radicals.
In addition to ethylene glycol or 1,4-butanediol radicals, the preferred polyalkylene terephthalates can contain 0 to 20 mole % of radicals of other aliphatic diols with 3 to 12 C atoms or cycloaliphatic diols with 6 to 12 C atoms, e.g. radicals of 1,3-propanediol, 2-ethyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 3-methyl-1,3- and -1,6-pentanediol, 2-ethyl-1,3-hexanediol, 2,2-diethyl-1,3-propanediol, 2,5-hexanediol, 1,4-di(xcex2-hydroxyethoxy)benzene, 2,2-bis(4-hydroxycyclohexyl)propane, 2,4-dihydroxy-1,1,3,3-tetramethylcyclobutane, 2,2-bis(3-xcex2-hydroxyethoxyphenyl)propane and 2,2-bis(4-hydroxypropoxyphenyl)propane (DE-OS 2 407 647, 2 407 776, 2 715 932).
The polyalkylene terephthalates can be branched by incorporating relatively small quantities of 3- or 4-hydric alcohols or 3- or 4-basic carboxylic acids, as described in DE-OS 1 900 270 and U.S. Pat. No. 3,692,744. Examples of preferred branching agents are trimesic acid, trimellitic acid, trimethylolethane and -propane and pentaerythritol. It is advisable to use no more than 1 mole % of the branching agent, based on the acid component.
Polyalkylene terephthalates which have been produced solely from terephthalic acid and its reactive derivatives (e.g. its dialkyl esters) and ethylene glycol and/or 1,4-butanediol and mixtures of these polyalkylene terephthalates are particularly preferred.
Preferred polyalkylene terephthalates are also copolyesters which have been produced from at least two of the above-mentioned alcohol components: particularly preferred copolyesters are poly(ethylene glycol 1,4-butanediol)terephthalates.
The polyalkylene terephthalates that are preferably suitable generally possess an intrinsic viscosity of 0.4 to 1.5 dl/g, preferably 0.5 to 1.3 dl/g, especially 0.6 to 1.2 dl/g, measured in phenol/o-dichlorobenzene (1:1 parts by weight) at 25xc2x0 C. in each case.
Suitable polyamides are known homopolyamides, copolyamides and mixtures of these polyamides. These can be partly crystalline and/or amorphous polyamides.
Polyamide 6, polyamide 6.6, mixtures and appropriate copolymers of these components are suitable as partially crystalline polyamides. In addition, partially crystalline polyamides the acid component of which consists wholly or partly of terephthalic acid and/or isophthalic acid and/or suberic acid and/or sebacic acid and/or azelaic acid and/or adipic acid and/or cyclohexanedicarboxylic acid, the diamine component of which consists wholly or partly of m- and/or p-xylylenediamine and/or hexamethylenediamine and/or 2,2,4-trimethylhexamethylenediamine and/or 2,4,4-trimethylhexamethylenediamine and/or isophorone diamine, and the composition of which is known in principle, can be considered.
In addition, polyamides can be mentioned which are produced wholly or partly from lactams with 7-12 C atoms in the ring, optionally incorporating one or more of the above-mentioned starting components.
Particularly preferred partially crystalline polyamides are polyamide 6 and polyamide 6.6 and mixtures thereof. Known products can be used as amorphous polyamides. They are obtained by polycondensation of diamines such as ethylenediamine, hexamethylenediamine, decamethylenediamine, 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine, m- and/or p-xylylenediamine, bis(4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)propane, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-diaminodicyclohexylmethane, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 2,5- and/or 2,6-bis(aminomethyl)norbornane and/or 1,4-diaminomethylcyclohexane with dicarboxylic acids such as oxalic acid, adipic acid, azelaic acid, decanedicarboxylic acid, heptadecanedicarboxylic acid, 2,2,4- and/or 2,4,4-trimethyladipic acid, isophthalic acid and terephthalic acid.
Copolymers obtained by polycondensation of several monomers are also suitable, as are copolymers produced with the addition of aminocarboxylic acids such as xcex5-aminocaproic acid, xcfx89-aminoundecanoic acid or xcfx89-aminolauric acid or their lactams.
Particularly suitable amorphous polyamides are the polyamides produced from isophthalic acid, hexamethylenediamine and other diamines such as 4,4xe2x80x2-diaminodicyclohexylmethane, isophorone diamine, 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine, 2,5- and/or 2,6-bis(aminomethyl)norbomene; or of isophthalic acid, 4,4xe2x80x2-diaminodicyclohexylmethane and xcex5-caprolactam; or of isophthalic acid, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-diaminodicyclohexylmethane and laurolactam; or of terephthalic acid and the isomer mixture of 2,2,4- and/or 2,4,4-trimethylhexamethylenediamine.
Instead of pure 4,4xe2x80x2-diaminodicyclohexylmethane, mixtures of the positional isomeric diaminodicyclohexylmethanes can also be used, which are composed of
70 to 99 mole % of the 4,4xe2x80x2-diamino isomer
1 to 30 mole % of the 2,4xe2x80x2-diamino isomer
0 to 2 mole % of the 2,2xe2x80x2-diamine isomer and
optionally correspondingly more highly condensed diamines, obtained by hydrogenation of technical grade diaminodiphenylmethane. The isophthalic acid can be replaced by up to 30% terephthalic acid.
The polyamides preferably have a relative viscosity (measured on a 1 wt. % solution in m-cresol at 25xc2x0 C.) of 2.0 to 5.0, particularly preferably 2.5 to 4.0.
If, in addition, other rubber-free thermoplastic resins not built up from vinyl monomers are used, the quantity of these is up to 500 parts by weight, preferably up to 400 parts by weight and particularly preferably up to 300 parts by weight (based on 100 parts by weight I)+II) in each case).
The modified polyalkylene ethers (II) within the meaning of the invention are prepared by treating polyethers with carboxylic acids and/or carboxylic anhydrides.
The polyalkylene ethers to be modified according to the invention are built up of di- and polyfunctional (cyclo)aliphatic radicals and may also contain small quantities of olefinic groups. Reaction products of diols or polyols, ethylene glycol, 1,2-propylene glycol, trimethylolpropane, glycerol, pentaerythritol, sorbitol and mannitol and one or more alkylene oxides, such as ethylene oxide and propylene oxide (for preparation and use, see Ullmanns Encyklopxc3xa4die der technischen Chemie, 4th edition, vol. 19, p. 31, Verlag Chemie, Weinheim 1980) are suitable. Polyalkylene ethers with large proportions of 1,2-propylene structures are preferred.
Both linear and branched polyalkylene ethers may be used, moderately branched and linear types being preferred.
The xe2x80x9cstartingxe2x80x9d, i.e. unmodified, polyalkylene ethers possess molecular weights (number average) of between 500 and 15,000, preferably between 1000 and 10,000 and particularly preferably between 2000 and 5000.
In principle, aliphatic, preferably with 1 to 20 carbon atoms, aromatic and araliphatic carboxylic acids and their anhydrides are suitable as carboxylic acids for treating the polyethers. Saturated and unsaturated mono-, di- and tricarboxylic acids may be used.
Examples of suitable carboxylic acids are formic acid, acetic acid, propionic acid, trimethylacetic acid, lauric acid, oleic acid, stearic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, benzoic acid, phenylacetic acid, o-, m- or p-toluic acid, phthalic acid, isophthalic acid, terephthalic acid.
Examples of suitable carboxylic anhydrides are acetic anhydride, maleic anhydride, phthalic anhydride.
In principle, carboxylic acid derivatives such as hydroxycarboxylic acids (e.g. glycolic acid, lactic acid, hydroxybutyric acid, glyceric acid, malic acid, tartaric acid, citric acid, mandelic acid, salicylic acid) or 2,2xe2x80x2-thiodiacetic acid and 3,3xe2x80x2-thiodipropionic acid are also suitable.
Preferred carboxylic acids within the meaning of the invention are formic acid, acetic acid, propionic acid, oxalic acid, benzoic acid, phthalic acid; formic acid, acetic acid, oxalic acid and benzoic acid are particularly preferred, and acetic acid is especially preferred.
Preferred carboxylic anhydrides within the meaning of the invention are acetic anhydride and phthalic anhydride.
The treatment of the polyalkylene ethers with carboxylic acid or carboxylic anhydride generally takes place at temperatures of 20xc2x0 C. to 100xc2x0 C., preferably of 25xc2x0 C. to 90xc2x0 C., particularly preferably 30xc2x0 C. to 80xc2x0 C. and especially preferably 40xc2x0 C. to 60xc2x0 C.
The quantity of carboxylic acid or carboxylic anhydride, based on the quantity of polyalkylene ethers, can be varied within broad limits. It is generally 0.01 to 3 wt. %, preferably 0.02 to 2 wt. % and particularly preferably 0.05 to 1 wt. %.
The modified polyalkylene ethers obtained according to the invention may be incorporated into the polymers to be provided with antistatic properties by known methods, e.g. by kneading, rolling or extruding together.
In addition to the antistatic agents according to the invention, the conventional additives such as e.g. pigments, fillers, stabilisers, lubricants, mould release agents, flame retardants and the like may also be added to moulding compositions.
The moulding compositions thus obtained are processed into finished parts, e.g. housing parts for domestic and electrical appliances, profile parts, films, car interior trim etc. by the conventional methods for thermoplastics.
The finished mouldings are distinguished by excellent antistatic properties and especially by deposit-free, homogeneous and glossy surfaces. The mechanical properties, especially the heat resistance and the impact resistance and, in particular, the flow properties when soft are virtually unimpaired compared with the unmodified material. The lustre of the mouldings is equally unaffected.